1339 Open Alliance Build Thread

Have you considered using 0.1" or 0.09" aluminum plate in place of 1/8"? We’ve found that the weight savings can be pretty significant on unpocketed plates, especially if your robot is primarily constructed out of tube and gusset.

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Yes, we’ve also used 1/10" plate and it’s fine, nothing wrong with making that choice. This year we had 1/8" on hand and the price of new metal made it the easiest choice for us.


Mid-/week Update, Week 3

We have had to make a few minor adaptations to the kinds of setbacks that typically happen in build season, but we are still doing well schedule-wise, and hope to have a fully assembled robot by the end of the day Saturday.

Our powder coating sponsor is in the middle of a major move, from a 10,000 sf facility to one more than double in size. This means they are backed up on jobs and couldn’t do their normal one-day turnaround, but rather would take two weeks or more. We appreciate their continued support but needed to make a quicker choice, so chose to paint it ourselves with automotive paints. We used acid-etch primer, regular primer, paint and a matte topcoat. We will definitely need to do touchup, as we have had to redrill some holes already. That’s okay!
The gearboxes seem to have been mis-cut. They are the same design we ran successfully on our fall drive base, but this time there is a definite “clocking” when the motor pinions interact with the first stage. It might be that the new CNC didn’t cut them right, or it might have been the speed of cut was too high, or it could be something else. In any case, we need to rebuild both drive boxes before finishing the install, which is annoying but not a huge deal (yet).
The weather was uncooperative yesterday, so we lost a day of work, as after-school activities were canceled. We also struggled with productivity on Monday. These things happen.

In any case, we are still pretty close to on target, and we believe we should have most of the robot functional soon. Here are some pictures of today’s progress for you. Thanks folks, hope your build season is going well.

Mr. N


Beautiful! Have you guys considered a sponsorship from Pepto-bismol?

CAD looks solid!


1726 built a nifty sort of long range shooter for 2009, spent a lot of time playing with vision and it worked great in our shop, but not on the field at our first regional. Near the end of the event, we finally figured out that if we just added a bit to our hood, and waited till we were on the opponents’ trailer to shoot, we could dump a load of balls in quickly, every time. Too late for that regional, but we qualified #1 and won our second regional. So yeah, going for the short, quick, reliable shot can be a good thing in some games.

Also…the robot is beautiful! thanks for sharing your design as you go. I just started reading, I’ll be sure to follow along now.

I love the lack of lightening holes…it’s the sensible way to build a robot.


Weekend Update, Week 3

Upcoming FUN Video Update

We are hoping that when we film with FUN on Tuesday night this week, we are able to give y’all information that you want and need from us. If you have any questions you’d like us to prepare for (including photographs, videos, programming questions, etc.) please let us know here or via PM before our meeting Tuesday afternoon, so we can prepare. Looking forward to seeing you then!


If you haven’t yet looked at the 7492 Build Blog, you should. This team is doing a super job in documenting their process, and the robot looks great. I keep seeing ways in which their process and their product are running parallel to ours this year. For instance, both of our teams are choosing to build many parts out of polycarbonate sheet rather than pocketed sheet aluminum. It makes machine time much, much less and is less expensive and lighter. We started doing this intentionally in 2020 (though we have often used a lot of polycarb before then) and honestly I don’t know yet what the disadvantages are, if they exist. In any case, 7492 is doing a fantastic job and their work will be helpful to any team wanting to learn stuff about this game.

What I Wish We’d Done Differently, Part 1

  1. Thin Wall Drive Rails. Using 1/8" stock has meant that our internal belt pulleys are harder to fit inside than we thought they would be, which was frustrating this week and may cause problems if and when the GT3 drive belts ever break. If we had used 1/16" stock I think this problem would have not occurred.
  2. Found a Practice Field in the Off Season. This is always the problem, isn’t it. I wish that we had found a place where, when this robot is mechanically and electrically complete (later this week, according to the schedule), we would be able to send the programmers and drive team to get in all those needed hours of practice. As it is we will have to put in precious hours trying to figure out a solution while we are in the midst of the build season.
  3. Not Written Off Pneumatics. Not that I want to use an entire other system that could fail catastrophically. It’s just that we’ve had to come up with some gear-and-sprocket workarounds that probably could have been lighter, faster, and more reliable if we just hadn’t said “no” so quickly. This choice might also affect our intake, which will deploy via servo and gas springs, and will stay down throughout the match. I understand there are risks involved here, that could have been mitigated with some pneumatics.

Plan for the Week

  1. Robot v1 should be mechanically complete on Tuesday, and fully wired on Wednesday. This means installing the climber subsystem and the intake, both of which are waiting on parts delivery (hopefully coming in on Monday, fingers crossed).
  2. Robot in the hands of the programmers for testing all systems on Saturday.
  3. Build Hangar and improve the Hub, with accurate placement of the Fenders.
  4. Procure some donated carpet, larger and more accurate than the piece we have rolled up in my classroom closet.
  5. Build the bumpers.
  6. Finish the team shirts, and continue to work on the sweatbands we are giving away at competition. Make the bumper numbers, the vanity bumper logos, the banners, and other Imagery-related things.
  7. Create the various Autonomous paths from each starting position.
  8. Get a Thrifty sponsorship.

    Have a great week, y’all.

Mr. N


Gorgeous work. Keep it up!

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Snow Day Update

School was canceled today due to an overnight snow storm that left about a foot of soft fluff all over Denver. We were not sure what our team meeting status would look like, but by noon the streets were pretty clear and we decided to have the shop open for anyone who was able to come in. Six students and a mentor were able to meet me, and together we got a lot done. The wiring all works and passes the tug test, though it still needs to be made more neat. The main breaker was wired up as well. The intake was assembled and installed, and we found that the tolerances were just a bit too tight, so we made a slight redesign and cut two new panels. The intake now fits beautifully, and it looks like we won’t even need the servo-initiated drop on the gas shock springs to start the match, as the assembly stays in place nicely on its own.

We were able to cut the plywood for the bumpers , and have now got the blue set bolted together using angle brackets, and the noodles are neatly taped down. The whole assembly fits, which is great. We’ll finish assembling the red set and the vanities on Saturday.

We’ve now finished setting the CAN ID’s, tested the intake for the first time, and are calling it a night.

What I Like
The new Rev PDH was very clean and easy to set up, and we really appreciate the extra 40A slots this year, since we decided not to run any pneumatics, and everything is built around motors.

We are also super impressed with the Rev Max Planetary gearboxes, and we are using them exclusively when we need reductions greater than a belt and pulley can provide.

Students Leading Each Other
This team has two lead mentors (including me), one professional programming mentor for ULA, and a couple of recent college grads who were team members back in the day. We’ve all experienced the brain drain that Covid has caused, and it has been amazing to me to see how our students have stepped up to train each other while simultaneously doing their own work on this robot build. We have probably the strongest group of Seniors in my memory, Including Isa our Imagery lead, Diego who leads Programming, Helen who is in charge of Manufacturing, Nick our Driver and head of Design and Strategy, and Julia the team Captain. Because of their dedication and hard work not only are we close to having a working robot mid-week 4, but we have an engaged group of younger students who are really learning the ropes and making major contributions. Getting a little choked up here. So much has gone wrong with the world over the last couple of years, and I’m really amazed at these young folks, who are some of the brightest of bright spots in these hard times.

I look forward to testing the full robot on Saturday, when we next meet. There’s certainly a lot that can go wrong, and I look forward to failing early so we can succeed later. Hope you are all having a safe and productive time.

Mr. N


This robot is totally radical! 1339 AngelBotics showcases their initial assembly, provides a CAD overview and details a PathWeaver Demo for Rapid React. https://youtu.be/PkwMCldNpLU



End of Week 4 Update

Much of our effort this weekend was focused on finalizing the assembly of our climber. As a result of much internal debate, we ended up painting the first stage of the extension element a new shade of green. After doing so we fully re-assembled the climbers and optimized their chain tension with half-links.

We cut out the first iteration of our hook designs for the climber and mounted them to both the static and dynamic climb elements. After a bit of sanding and filing, the carabineer hooks operate smoothly and only need to have a spring mounted to them before being complete.

In order to test the overall functionality of the extending climber, we set up the rigging and ran the spool. Aside from a bit of stickiness in the second climber stage, which was remedied with some lubrication, everything seemed to work well.


After receiving some falcon spline-to-hex adapters on Friday, we were able to fully belt up and assemble the power transmission for our shooter. We then cut, drilled, and ziptied some 1/8" polycarbonate sheet to the tubes comprising our shooter’s back wall, giving the balls a consistent, even surface to accelerate against.

Preliminary testing of the shooter seems to indicate that we will be able to make the upper and lower shots from against the fender quite consistently. The back wheel of our shooter offers ~20 degrees of adjustability in projectile angle. I’m not sure if this has already been stated, but we’re currently running 1.5" of compression.

Ball Path

Our singulation system has remained largely unchanged, except for a strip of nitrile tread which was added down its center near the front of the robot. This was largely a response to the intake geometry change, which necessitated greater compression directly behind the last intake roller. The nitrile strip was a quick and dirty proof of concept, and we’ll improve upon it in the next few days.

So far we’ve identified one dead zone in our robot, which is located in the center of the indexer. We think that the ball is getting stuck mostly because of the aforementioned nitrile tread, and the issue should resolve itself when we replace the tread with a better solution. If this does not prove sufficient, we’ll add some kind of tensioner to hold the belts inwards against the cargo.

Just as with the shooter, we added a polycarbonate backing to the indexer, ensuring constant compression as the ball moves through the S-Curve.


Assembly for the plywood components of all three sets of bumpers started today. One set is further along than the others, and will probably be complete in the next few days.

Work Space Update

A parent of one of our students volunteered to construct the hangar for our team and offered us a space to set up some field elements. Today a few members of our team traveled to the new space and set up a carpet. While we initially planned to test our climb there today, we weren’t yet confident in it, and instead opted to stay at the school and test the shooter.

In the next week or so we will tape out different areas of the field and build some improved versions of field elements to practice with.

It was great to see the robot come to life today for the first time. Although I’ve been through a few seasons of robotics now, the joy of seeing something you designed on a computer fulfill its purpose in real life never seems to get old. I hope everyone’s build season is going well, and am more than happy to answer any questions that you might have!



A few more images to share with y’all to go with Nick’s post.

We received a donation of carpet this weekend which was awesome.

A team parent is kindly allowing us to use their shop space as a practice field. We drove up to drop off the carpet and saw the narrow Hangar that he had built for us. Fantastic, very sturdy. Guaranteed to help us climb!

We spent some time this week with 8283, a team we value as the newest member of the Denver Public Schools crew. They are building a cool version of the Everybot, powered by all Neo motors. I am personally jealous of their teacher’s classroom size and machinery. Awesome stuff.


Here is a short video showing the ball path for a test fire. Ball was released at around 25% on both the top and main shooter wheels. Playing with the percentage with either results in very different flight trajectories.

Finally, just a pretty picture with the bumpers.

Mr. N


A Part of Our Success

An important but often overlooked part of building robots is the actual time spent building the robots. We have an awesome team, but I think one of the keys to our success this far in the season is our meeting times.

Pre-Covid, we used to meet 6 days a week, as long as possible after school, and full workdays on Saturdays. But this year, our schedule was cut down to 4 days. Now upon hearing this I was quite apprehensive. How would we get a robot done in 2/3s the time? It seems counterintuitive, but I think fewer workdays have contributed to our success. Now there is ample rest time, time to just take a break and collect our thoughts before embarking upon another week.

And with fewer meeting times, our meetings themselves have become more productive. Compared to years before, meeting 6 days a week, it seemed like we had all the time in the world, there was time to goof off a bit. But this year, with only 4 days, there is a sense of limited time, a bit of urgency that we need to keep moving and complete our goals. And so far it has worked. We are ahead of where we normally are and that is due to an awesome CAD team and more productive meetings. Might not work for all teams, just something to keep in mind.

And we even still find the time to have a bit of fun.



Planning outside of meetings and going hard for a couple hours with everyone there anecdotally looks like it works a lot better than “labs open 6-7 days, come thru!”

The secret ingredient is planning outside of meetings, IMO.


Your robot looks amazing! If you don’t mind me asking, do you have any fasteners/brackets holding down the top of the first telescope stage to prevent twisting? Thanks!

Great job! Looking forward to seeing it in action in a few weeks.

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End of Week 5 Update

The team continues to make progress, but now it tends to be in less obvious ways, and sometimes is partnered with setbacks. We have been affected, like many of you, by the news about Falcon motor quality control issues, and we spent a large portion of this week trying to organize disassembly and repair of Falcons while still using the robot in other ways. Sometimes this meant a loss of work time for programmers or drive team, and that effort and expertise among our mechanical crew that could have been used better was instead redirected to Falcons. I estimate we’ve put about 40 worker-hours into this, which is… not making me happy. At least we know we are in good company. In the end we found that the use of Loctite was rare (only four had any, and that was not consistent). Two were also missing the shims, one had an M3 screw that was held in place by… air, I guess, since it didn’t have teeth that would engage in the housing threads, and we stripped the screws on one motor, which we have set aside and will deal with later.

We are not having great luck with the color sensors as a replacement for beam breaks in lining up the balls pre-shooter. We will likely go back to using the same sensors we had on our 2020 robot to resolve this issue; I will post an edit here later when I verify what those sensors were, and will let you know if this swap fixes the problem.

We finished the bumpers this week. With most of our frame perimeter taken up with component attachment points, we decided to use rivnuts on each corner, with a 1/4-20 bolt and washer through a hole in a corner mounting plate. We have used similar solutions in past years and we think this is the right choice for this year. It is simple, secure, and I think it looks cool. It also makes it very simple for two people to swap bumpers in less than a minute.

We are planning on spending tomorrow with a limited team going to the practice field. The goal is to get real work done on the climb, and to test autonomous and drive as much as possible. I currently feel somewhat behind on this, because we’ve been chasing too many gremlins this week. I hope very much that tomorrow is productive!

That’s it for now, we will keep you posted about tomorrow’s progress. Hope you are all doing well.



Looks great! How much does it weigh?


Here are some videos of our testing on our practice field yesterday. I’ll try to make these instructive.


We spent a chunk of the day testing climbing using the “Lego” method. This video demonstrates the amount of tilt we experience. While cadding we were careful to locate the CoM near the physical center of the robot so as to avoid tipping and swinging during the climb.

Climb test 1339 https://imgur.com/gallery/7j7bLUP

Here is one of our climb tests. As you can see there are still some issues to work out, including an imbalance between spools, and a need to slightly redesign the passive hooks to release earlier. There is still very little swing which is good. We are using the Thrifty Bot climbers. Shortly after we took this we broke one of the 3D printed secondary stage internal stops. I strongly recommend getting the upgraded (solid print) versions of these, and of getting extras so that you can replace yours if they break. Thrifty is a great company to work with and will help get you fixed up. Other than the fragility of the early versions of the internals they are an excellent product.

Driving over a bump 1339 https://imgur.com/gallery/MtXHWVJ

We put 4" wheels on this robot, with no belly pan and no center drop. As you can see it does not struggle to get over a 7/8" obstacle, in case any of you worry about your ground clearance.

Ball pickup and shooting 1339 https://imgur.com/gallery/0RQavJH

We are not really finding it difficult to shoot accurately into either high or low goal. The lack of backspin due to top and bottom rollers means, as well as the relatively low energy shot from the fender, that these balls are unlikely to bounce out.

Testing acceleration control 1339 https://imgur.com/gallery/UeSxcNJ

One thing we are finding challenging is fixing the instantaneous acceleration from having the most powerful drive base we’ve ever run. Even with a pretty low COG (9"), it wants to get a bit tippy when accelerating or reversing. Trying different ways to fix this in the code.

Hope this is all helpful info! Have a great weekend.

Mr. N


Have you considered putting something like tread on either of the hooks to increase friction? That way you’re passively dampening the motion and reducing swing.

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Have you considered using the slew rate limiter?